Following the normal steps of running "./configure" and "make" to build Vim on an HP-UX 10.20 will result in Vim being linked with the termlib library. This library does not support certain termcap capability codes, such as the "Co" code used to query the number of colors supported by the terminal. Consequently, Vim will not display colors when used with a color terminal such as a color xterm.

One solution to this is to run the configure script with the "--with-tlib=curses" option, like this:

./configure --with-tlib=curses

This will cause Vim to be linked with the HP-UX curses library, which does support the color termcap capability codes.

Note that the xterm that comes standard with HP-UX 10.20 does not display color character attributes. To see colors when running Vim in a terminal window, you will also need to install a color terminal emulator such as a recent xterm.